Metallic glass

ABSTRACT

A metallic glass having a general formula of Zr15-65Cu0-25Ni0-20Al0-30Hf0-30Ti0-30Co0-30.

TECHNICAL FIELD

The invention relates to a metallic glass and a fabrication method thereof.

BACKGROUND

Metallic glass (MGs), also known as amorphous metals, are solid metallic materials with disordered atomic-scale structure. These non-crystalline structures have good electrical conductivity, and they also display superconductivity at low temperatures.

MGs have enormous structural, functional, and biomedical applications. One of the roadblocks against the wide deployment of MGs is their limited size, resulting from the poor glass forming ability (GFA) of MGs relative to that of other glassy systems, such as oxide glasses.

The development of new MGs, especially bulk metallic glasses (BMGs) with attractive mechanical and thermal properties, is still much needed today for industries.

SUMMARY

In a first aspect, there is provided a metallic glass which is metalloid-free, having a general formula of Zr₁₅₋₆₅Cu₀₋₂₅Ni₀₋₂₀Al₀₋₃₀Hf₀₋₃₀Ti₀₋₃₀Co₀₋₃₀.

The metallic glass may be a bulk metallic glass or a ribbon metallic glass. Optionally, the metallic glass may be in the form of a wire/ribbon (e.g., having an average thickness of about 10 μm to about 100 μm) or a rod (e.g., having an average diameter or an average thickness of about 1 mm to about 5 mm). The metallic glass may have a hardness of about 4 GPa to about 9 GPa. Preferably, the metallic glass is non-toxic.

Examples of a bulk metallic glass include: Zr_(59±2)Cu_(16±2)Ni_(12±2)Al_(10±2)Hf_(2.5±0.5)Ti_(0.5±0.3), Zr_(55±2)Cu_(20±2)Al_(15±2)Co_(10±1), Zr_(54±2)Ni_(16±2)Cu_(14±2)Ti_(10±2)Al_(6±1), Zr_(55±2)Cu_(20±2)Co_(10±2)Ti_(8±2)Al_(7±1), Zr_(55±2)Cu_(20±2)Ti_(10±1)Co_(10±1)Al_(5±1), or Zr_(45±2)Cu_(20±2)Ti_(10±2)Al_(10±2)Co_(10±2)Hf_(5±1), for example, Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2), Zr₅₅Cu₂₀Al₁₅Co₁₀, Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆, Zr₅₅Cu₂₀Co₁₀Ti₈Al₇, Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅, and Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅.

Examples of a ribbon metallic glass include: Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67), Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀, Zr₂₅Hf₂₅Al₂₅Co₂₅, Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀, Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67), and Ti₂₅Zr₂₅Hf₂₅Co₂₅.

In a second aspect, there is provided a method of fabricating a metallic glass having a general formula of Zr₁₅₋₆₅Cu₀₋₂₅Ni₀₋₂₀Al₀₋₃₀Hf₀₋₃₀Ti₀₋₃₀Co₀₋₃₀, which may be a bulk metallic glass or a ribbon metallic glass. The metallic glass may be the metallic glass of the first aspect.

To fabricate a bulk metallic glass, the method includes melting a mixture essentially consisting of, in atomic percentage, about 15% to about 65% of Zr, 0% to about 25% of Cu, 0% to about 20% of Ni, 0% to about 30% of Al, 0% to about 30% of Hf, 0% to about 30% of Ti, 0% to about 30% of Co; and quenching the molten mixture in a mold to form a casted, bulk metallic glass. Preferably, the melting is performed in an arc-melting furnace with a vacuum level of up to 8×10⁻⁴ Pa.

To fabricate a ribbon metallic glass, the method may be similar to the above method for fabricating a bulk metallic glass, except after the step of quenching the molten mixture in a mold to form a casted metallic glass, the method further includes melting the casted metallic glass and melt spinning the molten mixture to form the ribbon metallic glass. Preferably, the melt spinning is performed in an induction-melting furnace with a vacuum level of up to 8×10⁻⁴ Pa, and optionally, at a rotating speed of about 60 r/s to about 90 r/s, preferably at about 75 r/s.

In a third aspect, there is provided an article comprising a metallic glass having a general formula of Zr₁₅₋₆₅Cu₀₋₂₅Ni₀₋₂₀Al₀₋₃₀Hf₀₋₃₀Ti₀₋₃₀Co₀₋₃₀. The article may be a watch part, a surface coating, a part of medical equipment, or a part of sports equipment. The article may be manufactured using additive manufacturing.

Other features and aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. Any feature(s) described herein in relation to one aspect or embodiment may be combined with any other feature(s) described herein in relation to any other aspect or embodiment as appropriate and applicable.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an image of six bulk metallic glasses in accordance with one embodiment of the invention;

FIG. 2A is an image of Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67) ribbon metallic glass in accordance with one embodiment of the invention;

FIG. 2B is an image of Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀ ribbon metallic glass in accordance with one embodiment of the invention;

FIG. 2C is an image of Zr₂₅Hf₂₅Al₂₅Co₂₅ ribbon metallic glass in accordance with one embodiment of the invention;

FIG. 2D is an image of Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀ ribbon metallic glass in accordance with one embodiment of the invention;

FIG. 2E is an image of Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67) ribbon metallic glass in accordance with one embodiment of the invention;

FIG. 2F is an image of Ti₂₅Zr₂₅Hf₂₅Co₂₅ ribbon metallic glass in accordance with one embodiment of the invention;

FIG. 3 is a graph showing the GFA values of the glass-forming alloys predicted using the rational quadratic kernel GPR (RQGPR) model;

FIG. 4A shows the X-ray diffraction (XRD) spectra of the bulk metallic glasses and the ribbon metallic glasses;

FIG. 4B shows the X-ray diffraction (XRD) spectra of the glass-forming alloys of low glass forming ability in Φ2 mm rods;

FIG. 5A shows the differential scanning calorimetry (DSC) curves of the bulk metallic glasses;

FIG. 5B shows the differential scanning calorimetry (DSC) curves of the ribbon metallic glasses at low temperatures;

FIG. 5C shows the differential scanning calorimetry (DSC) curves of the ribbon metallic glasses at high temperatures;

FIG. 6 is a graph of T_(g) against T_(l) of reported metallic glasses and the bulk metallic glasses and the ribbon metallic glasses;

FIG. 7 is a graph of T_(rg) against γ of the bulk metallic glasses and the ribbon metallic glasses;

FIG. 8A shows the atom probe tomography (APT) elemental maps of Zr₂₅Hf₂₅Al₂₅Co₂₅ ribbon metallic glass;

FIG. 8B shows the atom probe tomography (APT) elemental maps of Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ bulk metallic glass;

FIG. 9A is the transmission electron microscopy (TEM) image of Zr₂₅Hf₂₅Al₂₅Co₂₅ ribbon metallic glass, where the inset is the selected area diffraction pattern;

FIG. 9B is the high resolution transmission electron microscopy (HRTEM) image of Zr₂₅Hf₂₅Al₂₅Co₂₅ ribbon metallic glass;

FIG. 9C is the bright field scanning transmission electron microscopy (STEM) image of Zr₂₅Hf₂₅Al₂₅Co₂₅ ribbon metallic glass, where the inset shows the HRTEM image at the same size scale;

FIG. 9D is the transmission electron microscopy (TEM) image of Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ bulk metallic glass, where the inset is the selected area diffraction pattern;

FIG. 9E is the high resolution transmission electron microscopy (HRTEM) image of Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ bulk metallic glass; and

FIG. 9F is the bright field scanning transmission electron microscopy (STEM) image of Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ bulk metallic glass, where the inset shows the HRTEM image at the same size scale.

DETAILED DESCRIPTION

Unless otherwise specifically provided, all tests herein are conducted at standard conditions which include a room and testing temperature of 25° C., sea level (1 atm.) pressure, pH 7, and all measurements are made in metric units. Furthermore, all percentages, ratios, etc. herein are by weight, unless specifically indicated otherwise. It is understood that unless otherwise specifically noted, the materials, compounds, chemicals, etc. described herein are typically commodity items and/or industry-standard items available from a variety of suppliers worldwide.

Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Terms of degree, such as “about” are understood by those of ordinary skill to refer to reasonable ranges outside of the given value, for example, general tolerances associated with manufacturing, assembly, testing, and use of the described embodiments.

As used herein, the term “metallic glass” refers to a material containing one or more glass-forming alloys. The glass-forming alloy may have a relatively high glass forming ability (GFA) for producing a bulk metallic glass (BMG) (e.g., having an average diameter or an average thickness of at least 1 mm). Alternatively, a ribbon metallic glass (RMG) (e.g., having an average thickness of about 10 nm to about 100 nm) may be produced from a glass-forming alloy has a relatively low GFA.

In one embodiment, a machine learning algorithm is used to project different multicomponent MGs. The algorithm comprises calculating factors of different stable compounds. The metallic glass may be a BMG or a RMG depending on the composition of the glass-forming alloys. Metallic glasses obtained by the algorithm has a general formula of Zr₁₅₋₆₅Cu₀₋₂₅Ni₀₋₂₀Al₀₋₃₀Hf₀₋₃₀Ti₀₋₃₀Co₀₋₃₀. In an alternative embodiment, the metallic glass may include additional transition metals, such as Fe and Nb. The metallic glasses may further include unavoidable impurities. These metals are non-toxic and easy to access (containing no rare earth metals or precious metals), thus offering substantial economic values. Due to the absence of any metalloid, toxic or noble element, these MGs may be used in wearables and biomedical applications including manufacturing (e.g., by additive manufacturing or other known techniques) of watch parts, surface coatings, medical equipment, or sports equipment.

The metallic glass may include, by atomic percentage, about 15% to about 65%, about 15.5% to about 62%, or about 16% to about 60% Zr. In one embodiment, the BMG may include at least 40%, at least 42%, or at least 45% Zr. The RMG may include at least 15%, at least 15.5%, or at least 16% Zr.

The metallic glass may include, by atomic percentage, 0% to about 25%, about 10% to about 23%, or about 13% to about 20% Cu. In one embodiment, the BMG may include at least 10%, at least 12%, or at least 13% Cu. The RMG may include 0%, at least 10%, or at least 15% Cu.

The metallic glass may include, by atomic percentage, 0% to about 20%, about 5% to about 18%, or about 10% to about 17% Ni. In one embodiment, the BMG may include 0%, at least 10%, or at least 12% Ni. The RMG may include 0%, at least 13%, or at least 15% Ni.

The metallic glass may include, by atomic percentage, 0% to about 30%, about 3% to about 28%, or about 5% to about 27% Al. In one embodiment, the BMG may include at least 1%, at least 3%, or at least 5% Al. The RMG may include 0%, at least 15%, or at least 17% Al.

The metallic glass may include, by atomic percentage, 0% to about 30%, about 1% to about 28%, or about 2% to about 26% HE In one embodiment, the BMG may include 0%, at least 1%, or at least 2% Hf. The RMG may include at least 10%, at least 12%, or at least 16% Hf.

The metallic glass may include, by atomic percentage, 0% to about 30%, about 0.1% to about 27%, or about 0.2% to about 26% Ti. In one embodiment, the BMG may include 0%, at least 0.1%, or at least 0.2% Ti. The RMG may include 0%, at least 15%, or at least 16% Ti.

The metallic glass may include, by atomic percentage, 0% to about 30%, about 5% to about 27%, or about 9% to about 25% Co. In one embodiment, the BMG may include 0%, at least 5%, or at least 9% Co. The RMG may include at least 10%, at least 15%, or at least 16% Co.

In one embodiment where the metallic glass is a BMG, the BMG is selected from the group consisting of: Zr_(59±2)Cu_(16±2)Ni_(12±2)Al_(10±2)Hf_(2.5±0.5)Ti_(0.5±0.3), Zr_(55±2)Cu_(20±2)Al_(15±2)Co_(10±1), Zr_(54±2)Ni_(16±2)Cu_(14±2)Ti_(10±2)Al_(6±1), Zr_(55±2)Cu_(20±2)Co_(10±2)Ti_(8±2)Al_(7±1), Zr_(55±2)Cu_(20±2)Ti_(10±1)Co_(10±1)Al_(5±1), and Zr₄₅₊₂Cu_(20±2)Ti_(10±2)Al_(10±2)Co_(10±2)Hf_(5±1). Additionally or alternatively, the BMG or RMG is selected from the group consisting of: Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2), Zr₅₅Cu₂₀Al₁₅Co₁₀, Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆, Zr₅₅Cu₂₀Co₁₀Ti₈Al₇, Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅, Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅, Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67), Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀, Zr₂₅Hf₂₅Al₂₅Co₂₅, Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀, Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67), and Ti₂₅Zr₂₅Hf₂₅Co₂₅. Unless otherwise specified, the atomic masses or percentages used herein refer to the particular value ±2%.

The metallic glass may have a reduced modulus of about 70 GPa to about 140 GPa, about 75 GPa to about 138 GPa, or about 80 GPa to about 135 GPa. In one embodiment, the BMG may have a reduced modulus of at least 90 GPa, at least 92 GPa, or at least 93 GPa. The RMG may have a reduced modulus of at least 70 GPa, at least 75 GPa, or at least 80 GPa. The metallic glass may have a hardness of about 3 GPa to about 10 GPa, about 3.5 GPa to about 9.5 GPa, or about 4 GPa to about 9 GPa. In one embodiment, the BMG may have a hardness of at least 5 GPa, at least 5.5 GPa, or at least 5.8 GPa. Compared with conventional alloys, such as steel, copper alloys, magnesium alloys and aluminium alloys, the BMGs of the present embodiments may have an outperforming hardness value of about 6 GPa to about 9 GPa. The RMG may have a hardness of at least 4 GPa, at least 4.5 GPa, or at least 4.7 GPa.

The metallic glass may have a glass transition temperature of about 600 K to about 850 K, about 605 K to about 840 K, or about 606 K to about 830 K. In one embodiment, the BMG may have a glass transition temperature of at least 610 K, at least 615 K, or at least 616 K. The RMG may have a glass transition temperature of at least 600 K, at least 605 K, or at least 606 K.

In one embodiment, the metallic glass (BMG or RMG) may be fabricated by melting a mixture essentially consisting of, in atomic percentage, about 15% to about 65% of Zr, 0% to about 25% of Cu, 0% to about 20% of Ni, 0% to about 30% of Al, 0% to about 30% of Hf, 0% to about 30% of Ti, and 0% to about 30% of Co; and quenching the molten mixture.

Preferably, the BMG is in the form of a rod having an average diameter or an average thickness of about 2 mm to 5 mm, and the RMG is in the form of a ribbon with an average thickness of about 50 nm. Alternatively, the BMG and RMG may have other shapes and sizes.

The raw materials used in the mixture may have a purity of higher than 95%, 97%, 99%, and preferably higher than 99.95%. The raw materials may be provided in the form of ingots, wires, powder, etc.

The melting may be performed in a furnace (e.g., an arc-melting furnace, an induction-melting furnace, a resistance-melting furnace, etc.) which may be pre-pumped and evacuated with vacuum prior to back-filling with inert gas (e.g., argon, nitrogen, helium, or any combination thereof). The vacuum level may be set to about 5×10⁻⁴ Pa, about 7×10⁻⁴ Pa, or about 8×10⁻⁴ Pa to avoid possible oxidation. The melting may be repeated for enhanced homogeneity. For example, the molten mixture may be remelted for at least 3 times or at least 5 times, and preferably 6 times.

The quenching may be performed with the use of a mold (e.g., a water-cooled mold) to form a casted metallic glass, e.g., a casted BMG. For example, the mold may be a copper mold having a diameter of 2 mm, 3 mm, or 5 mm. To fabricate RMG, the casted metallic glass may further be melted in a furnace and then subjected to melt spinning. Similar to the above, the furnace may be an arc-melting furnace, an induction-melting furnace, a resistance-melting furnace, etc. that is pre-pumped and evacuated with vacuum prior to back-filling with inert gas. The melt spinning may be performed with a copper wheel that is rapidly rotated at a rotating speed of about 60 r/s to about 90 r/s, or about 70 r/s to about 80 r/s, and preferably about 75 r/s.

Hereinafter, the present invention is described more specifically by way of examples, but the present invention is not limited thereto.

Unless otherwise specified, each of the raw materials for the MGs in the following examples has a purity level of higher than 99.95%. DSC experiments are performed using both DSC3/700 and TGA DSC3+HT/1600 (METTLER TOLEDO) with a heating rate of 20 K/min and argon flow with a rate of 50 mL/min. For scanning transmission electron microscope (STEM) experiments, STEM samples are prepared by PIPS II MODEL 695 (GANTAN) and the experiments are carried out using a JEM-ARM300F transmission electron microscope equipped with double spherical aberration correctors. For atom probe tomography (APT) experiments, needle-shaped APT specimens are fabricated by lift-outs and annular milled in a FEI Scios focused ion beam/scanning electron microscope (FIB/SEM). The APT characterizations are performed in a local electrode atom probe (CAMEACA LEAP 5000 XR). The specimens are analyzed at 70 K in voltage mode, at a pulse repetition rate of 200 kHz, a pulse fraction of 20%, and an evaporation detection rate of 0.2% atom per pulse. Imago Visualization and Analysis Software (IVAS) version 3.8 is used for creating the 3D reconstructions and data analysis.

Preparation of BMGs

Pure metals, including Ti, Zr, Hf, Al, Co, Ni, and Cu are used to prepare six BMGs having a general formula of Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2), Zr₅₅Cu₂₀Al₁₅Co₁₀, Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆, Zr₅₅Cu₂₀Co₁₀Ti₈Al₇, Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅, and Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅. The raw materials (including Ti ingots) are first melted in a lab-scale arc-melting furnace under an argon atmosphere that is pre-pumped to a high vacuum level of 8×10⁻⁴ Pa. After 6 times of remelting, the molten samples are then casted in copper molds. Specifically, Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅ and Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅ are casted in a copper mold with dimensions of Φ2 mm; Zr₅₅Cu₂₀Al₁₅Co₁₀, Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆, and Zr₅₅Cu₂₀Co₁₀Ti₈Al₇ are casted in a copper mold with dimensions of Φ3 mm; and Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2) is casted in a copper mold with dimensions of Φ5 mm to form the rod-shaped BMGs, as shown in FIG. 1 .

Preparation of RMGs

Pure metals, including Ti, Zr, Hf, Al, Co, Ni, and Cu are used to prepare six RMGs having a general formula of Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67), Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀, Zr₂₅Hf₂₅Al₂₅Co₂₅, Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀, Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67), and Ti₂₅Zr₂₅Hf₂₅Co₂₅. The raw materials (including Ti ingots) are first melted in a lab-scale arc-melting furnace under an argon atmosphere that is pre-pumped to a high vacuum level of 8×10⁻⁴ Pa. After 6 times of remelting, the molten ingot samples are then casted in copper molds. The casted ingots are then melted in a lab-scale induction-melting furnace under an argon atmosphere that is pre-pumped to a high vacuum level of 8×10⁻⁴ Pa. The molten ingots are then subjected to melt spinning with a single copper roller at a rotating speed of 75 r/s to form the RMGs, as shown in FIGS. 2A to 2F.

Characterization of the BMGs and RMGs

FIG. 3 shows the glass forming abilities (GFAs) of the above twelve BMGs and RMGs predicted by a machine learning model, namely the rational quadratic kernel GPR (RQGPR) model, in terms of ln(D). This regression machine learning model is characterized by low error and high coefficient of determination (about 0.8). The results confirm that all twelve BMGs and RMGs have a promising glass forming ability. It is worth noting that the atomic fraction of each constituent element varies over a wide range during the deep search of the compositional space for MGs.

FIGS. 4A and 4B show the X-ray diffraction (XRD) spectra of the above glass-forming alloys. The results clearly show that the twelve glass-forming alloys can form glass in either bulk or ribbon (or both). Specifically, the six glass-forming alloys with high GFAs could form glass in bulk. In contrast, the six glass-forming alloys with low GFAs could only form glassy ribbons, although they are crystallized in bulk (FIG. 4B).

The chemical composition of the glass-forming alloys is measured with energy dispersive X-ray spectroscopy (EDX). As shown in Table 1, the results show that the exact composition is consistent with the predicted composition (using the machine learning model) within a relative error of 9%.

TABLE 1 The EDX results of the twelve MGs. Zr Cu Ni Al Hf Ti Co Composition at % at % at % at % at % at % at % Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2) 59.2 16.1 12.2 10.1 2.2  0.2 — Zr₅₅Cu₂₀Al₁₅Co₁₀ 55.3 19.2 — 15.7 — — 9.9 Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ 53.9 13.8 15.9 6.1 — 10.3 — Zr₅₅Cu₂₀Co₁₀Ti₈Al₇ 56.0 19.0 — 7.2 —  8.1 9.7 Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅ 55.3 19.2 — 5.1 — 10.3 10.0 Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅ 45.0 19.6 — 10.4 5.4 10.0 9.6 Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67) 17.0 16.2 15.9 18.2 16.6 — 16.0 Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀ 19.7 19.5 — 21.1 20.4 — 19.4 Zr₂₅Hf₂₅Al₂₅Co₂₅ 24.5 — — 26.9 24.9 — 23.6 Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀ 19.5 — — 21.0 20.2 20.1 19.3 Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67) 16.2 — 16.2 17.7 17.0 16.8 16.0 Ti₂₅Zr₂₅Hf₂₅Co₂₅ 24.7 — — — 25.3 25.7 24.3

FIGS. 5A to 5C show differential scanning calorimetry (DSC) curves of the BMG and the RMGs. Table 2 show the glass transition temperature (T_(g)), the crystallization onset temperature (T_(x)), and the liquidus temperature (T_(l)) of the MGs obtained by DSC or by calculation. Calculations are performed with the following equations:

$\begin{matrix} {T_{g} = {\frac{M\sigma_{y}}{50\rho_{0}} + T_{0}}} & \left( {{Equation}1} \right) \end{matrix}$

where T_(g) is the glass transition temperature, M is the molar mass, σ_(y) is the yielding strength, ρ₀ is the density at the ambient temperature, and T₀ is the ambient temperature (298 K). M and ρ₀ are calculated directly from the composition of the MGs. Reduced modulus and hardness are measured via nanoindentation. Yielding strength σ_(y) is correlated to the measured hardness by:

σ_(y)=H/3  (Equation 2)

TABLE 2 The mechanical and thermal properties of the twelve MGs. Reduced modulus Hardness T_(g) T_(x) T_(m) T_(l) Compositions (GPa) (GPa) (K) (K) (K) (K) Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2) 99.28 6.41 657 750 1055 1165 Zr₅₅Cu₂₀Al₁₅Co₁₀ 113.50 7.07 695 769 1163 1225 Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ 93.20 5.89 616 676 1063 1104 Zr₅₅Cu₂₀Co₁₀Ti₈Al₇ 95.46 5.94 640 691 1084 1171 Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅ 96.18 5.89 631 672 1074 1145 Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅ 125.13 8.67 830 870 1109 1224 Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67) 130.27 8.41 764 830 1506 1625 (calculated) Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀ 134.38 8.80 677 810 1201 1487 Zr₂₅Hf₂₅Al₂₅Co₂₅ 111.16 7.72 808 866 1345 1649 Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀ 117.71 7.25 763 765 1336 1627 (calculated) Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67) 123.85 7.77 756 797 1380 1550 (calculated) Ti₂₅Zr₂₅Hf₂₅Co₂₅ 80.22 4.76 606 650 1229 1286 (calculated)

FIG. 6 is a graph of T_(g) against T_(l) of various reported metallic glasses and the twelve MGs. The ratio of T_(g)/T_(l)—also termed as the “reduced glass transition temperature, T_(rg)”—scales positively with the GFA of the MGs. As shown, there is a clear trend that T_(g)˜0.63 T_(l), within a margin of ±0.05 T_(l) for different classes of MGs. The high entropy RMGs are clearly off this trend because of their relatively high T_(l) or low T_(g)/T_(l) ratio.

Further, based on the DSC results, the T_(rg) and

$\gamma = \frac{T_{x}}{T_{g} + T_{l}}$

of the twelve MGs are also calculated. As shown in FIG. 7 , the results reaffirm that the GFA of the high entropy MGs is low, which can be attributed to the high thermal stability (high T_(l)) of their corresponding crystals.

Next, as examples, the amorphous structures of Zr₂₅Hf₂₅Al₂₅Co₂₅ RMG and Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ BMG are examined across the micro-, nano- and atomic-scale through 3D atom probe tomography (APT) and aberration corrected transmission electron microscopy. FIGS. 8A and 8B show the APT elemental mapping images; FIGS. 9A and 9D show the TEM images of the RMG and the BMG respectively; FIGS. 9B and 9E show the HRTEM images of the RMG and the BMG respectively; and FIGS. 9C and 9F show the TEM images of the RMG and the BMG respectively. It can be seen that both Zr₂₅Hf₂₅Al₂₅Co₂₅ and Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ show structural homogeneity at the nano-scale (FIGS. 8A and 8B). In addition, structural homogeneity is observed by the TEM and HRTEM results as well (FIGS. 9A, 9B, 9D and 9E). Interestingly, the STEM image of the Zr₂₅Hf₂₅Al₂₅Co₂₅ RMG (FIG. 9C) shows a clear sub-nano-scale chemical fluctuation which cannot be resolved by APT and TEM owing to their limited spatial resolution (1-2 nm). It is believed that this contrast can be attributed to a density fluctuation, which can result from excessive plasticity or simply signals an unusual capacity of a MG for plastic flows. In contrast, the STEM image of the Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ BMG (FIG. 9F) displays structural homogeneity in atomic-scale. Evidently, these findings demonstrate that the Zr₂₅Hf₂₅Al₂₅Co₂₅ RMG can afford a higher degree of chemical fluctuation than the Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆ BMG.

The above embodiments provide a variety of novel compositional complex metallic glasses with good mechanical properties (good castability and hardness) and thermal stability, e.g., for their wide supercool liquid region. In particular, the Zr-based BMGs have high hardness, good fluidity, good thermal stability and are easy to fabricate by one-time molding.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The described embodiments of the invention should therefore be considered in all respects as illustrative, not restrictive. 

1. A metallic glass having a general formula of Zr₁₅₋₆₅Cu₀₋₂₅Ni₀₋₂₀Al₀₋₃₀Hf₀₋₃₀Ti₀₋₃₀Co₀₋₃₀.
 2. The metallic glass of claim 1, wherein the metallic glass is a bulk metallic glass.
 3. The metallic glass of claim 2, wherein the metallic glass is selected from the group consisting of: Zr_(59±2)Cu_(16±2)Ni_(12±2)Al_(10±2)Hf_(2.5±0.5)Ti_(0.5±0.3), Zr_(55±2)Cu_(20±2)Al_(15±2)Co_(10±1), Zr_(54±2)Ni_(16±2)Cu_(14±2)Ti_(10±2)Al_(6±1), Zr_(55±2)Cu_(20±2)Co_(10±2)Ti_(8±2)Al_(7±1), Zr_(55±2)Cu_(20±2)Ti_(10±1)Co_(10±1)Al_(5±1), and Zr_(45±2)Cu_(20±2)Ti_(10±2)Al_(10±2)Co_(10±2)Hf_(5±1).
 4. The metallic glass of claim 3, wherein the metallic glass is selected from the group consisting of: Zr_(59.2)Cu_(16.2)Ni_(12.6)Al_(9.6)Hf_(2.2)Ti_(0.2), Zr₅₅Cu₂₀Al₁₅Co₁₀, Zr₅₄Ni₁₆Cu₁₄Ti₁₀Al₆, Zr₅₅Cu₂₀Co₁₀Ti₈Al₇, Zr₅₅Cu₂₀Ti₁₀Co₁₀Al₅, and Zr₄₅Cu₂₀Ti₁₀Al₁₀Co₁₀Hf₅.
 5. The metallic glass of claim 2 in the form of a rod.
 6. The metallic glass of claim 5, wherein the metallic glass has an average diameter of about 1 mm to about 5 mm.
 7. The metallic glass of claim 1, wherein the metallic glass is a ribbon metallic glass.
 8. The metallic glass of claim 7, wherein the metallic glass is selected from the group consisting of: Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67)Cu_(16.67), Zr₂₀Hf₂₀Al₂₀Co₂₀Cu₂₀, Zr₂₅Hf₂₅Al₂₅Co₂₅, Ti₂₀Zr₂₀Hf₂₀Al₂₀Co₂₀, Ti_(16.67)Zr_(16.67)Hf_(16.67)Al_(16.67)Co_(16.67)Ni_(16.67), and Ti₂₅Zr₂₅Hf₂₅Co₂₅.
 9. The metallic glass of claim 1, wherein the metallic glass has an average thickness of about 10 μm to about 100 μm.
 10. The metallic glass of claim 1 having a hardness of about 4 GPa to about 9 GPa.
 11. The metallic glass of claim 1, wherein the metallic glass is non-toxic.
 12. The metallic glass of claim 1, wherein the metallic glass is metalloid-free.
 13. A method of fabricating the metallic glass of claim 1, comprising: melting a mixture essentially consisting of, in atomic percentage, about 15% to about 65% of Zr, 0% to about 25% of Cu, 0% to about 20% of Ni, 0% to about 30% of Al, 0% to about 30% of Hf, 0% to about 30% of Ti, and 0% to about 30% of Co; and quenching the molten mixture in a mold to form a casted metallic glass.
 14. The method of claim 13, wherein the melting is performed in an arc-melting furnace with a vacuum level of up to 8×10⁻⁴ Pa.
 15. The method of claim 13, wherein the metallic glass is a ribbon metallic glass, and the method further includes: melting the casted metallic glass; and melt spinning the molten mixture.
 16. The method of claim 15, wherein the melt spinning is performed in an induction-melting furnace with a vacuum level of up to 8×10⁻⁴ Pa.
 17. The method of claim 15, wherein the melt spinning is performed at a rotating speed of about 60 r/s to about 90 r/s. 